Determining the fat content of milk

ABSTRACT

A batch of an oil-in-water emulsion such as milk or a milklike substance is stabilized by the addition of a viscosity increasing agent, a portion of the batch is analyzed to determine the fatty content thereof and the remainder of the stabilized batch is then utilized as a reference standard for checking and calibrating apparatus which is used to determine the fatty content of such emulsions by the light transmission characteristics thereof.

0 Unite m States Patent:

[72] Inventor Hanne Werner Helsingor, Denmark [2!] Appl. No. 790,931[22] Filed Jan. 14, 1969 [45] Patented Dec. 21,197] [73] Assignee N.Foss Electric AIS l-lillerod, Denmark [32] Priority Jan. 17, 1968 [33]Denmark [3| 154/68 [54] DETERMINING THE FAT CONTENT OF MILK 3 Claims, 2Drawing Flgs.

I52] U.S.Cl 23/23], 99/54, 99/60, 99/15 I [SI] Int. Cl G0ln 33/04, A23c3/08 [50] Field of Search 99/54, 60,

[56] References Cited UNITED STATES PATENTS 2,568,369 9/l95l Scholz99/130 2,844,067 7/l958 Borg 23/23l 3,054,678 9/1962 Michencr et al...99/l5l X 3,404.987 l0/l968 Kooistra et al 99/l5l X 3,434,846 3/l969Scott 99/54 X FOREIGN PATENTS 609,282 I l/l960 Canada 99/54 PrimaryExaminer Lionel M. Shapiro Assistant ExaminerD. M. NalfAttorney-Lackenbach & Lackenbach ABSTRACT: A batch of an oil-in-wateremulsion such as milk or a milklike substance is stabilized by theaddition of a viscosity increasing agent, a portion of the batch isanalyzed to determine the fatty content thereof and the remainder of thestabilized batch is then utilized as a reference standard for checkingand calibrating apparatus which is used to determine the fatty contentof such emulsions by the light transmission characteristics thereof.

PATENTED M82119?! 3,628,916

A .5 r 3% N3 BY Ma ATTORNEYS DETERMINING THE FAT CONTENT OF MILK Thisinvention relates to a preparation for controlling and adjusting anapparatus of the type used for determining the fatty content of anoil-in-water emulsion by measuring the physical properties of theemulsion such as sound or light transmission, a process for preparingsaid preparation, and a method for its application.

The known art comprises apparatus which determine the fatty content ofan oil-in-water emulsion by measuring the physical properties of theemulsion such as sound or light transmission, but generally suchapparatus are not stable over prolonged periods and require control andadjustment from time to time. Up to now this control has requiredcomplicated and time-consuming laboratory methods, and the adjustmentcould not therefore be made continuously, which has reduced theapplicability of the apparatus.

The air of the present invention is to provide a preparation havingstabilized physical properties, which preparation, after determinationof its fatty content in an accurately adjusted apparatus or byconventional analytic methods, can be used for continuous control andadjustment or other similar apparatus.

This has been achieved by the preparation according to the inventionwhich consists of an oil-in-water emulsion admixed with a stabilizingagent for maintaining the emulsified state.

As the said apparatus are usually intended for determining emulsions ofa certain type and would render inaccurate results for emulsions ofdifferent types the preparation according to the invention mayadvantageously contain an emulsion of the same type as normallydetermined in the apparatus.

As stabilizing agent may be used any agent capable of main taining theemulsion in a stable state at room temperature and below, but which maybe restored to the normal liquid state of the emulsion, for instance bychanging the pH value of the preparation or by heating. According to theinvention the preparation may conveniently contain a gelling agent ofthe type which causes the preparation to set at room temperature andbelow but restores the normal liquid state of the emulsion on beingheated. Examples of such gelling agents are gelatine, carrageenanes,pectins, and agar-agar.

According to the invention gelatine has proved particularly suitable asgelling agent, as the preparation made therewith possesses a good gelconsistency without any tendency to separation of liquid and afterheating to melting temperature has a consistency approximately like thatof the original emulslon.

The present invention is particularly intended for use in connectionwith the apparatus for rapid determination of the fatty content of milkdeveloped by applicants in the present application and sold under thename of Milko-Tester. The determination of the fatty content in aMilko-Tester is based on the ability of the milk-fat globules to diffuseand absorb part of the light transmitted through a milk sample. Theprinciple of determining the fatty content is a measurement of theamount of light capable of penetrating a milk sample homogenized anddiluted with a special liquid containing inter alia protein-dissolvingtetrasodium salt of ethylene diamine tetraacetate (trade name: Versene).The more fat globules the milk contains the more the light will bediffused. By measuring the light transmitted through milk samples whoseprotein has been dissolved values are obtained which bear a certainrelation to the fatty content of the milk sample. The principal reasonwhy this relation is not complete is the phenomenon known fromhomogenized milk wherein the finely divided fat globules make the milkwhiter in color because the many minute fat globules of the homogenizedmilk cause a greater diffusion of light than the smaller number of largefat globules of the nonhomogenized milk, and therefore milk sampleshaving the same fatty content will produce different results whenmeasured by light transmission where the size distribution of the fatglobules varies. To equalize this source of error the milk ishomogenized in four steps in the Milko-Testen The actual measuring ofthe light transmitted through the prehomogenized and diluted milksamples takes place while the samples pass a cuvette which is hit bylight having a wavelength of about 600 nm. The penetrating light isregistered by a photoelectric cell connected to a galvanometer whereinthe scale is divided directly into fat percent.

A disadvantage in using the Milko-Tester is that previously it was notpossible to control accurately and rapidly whether the reading of theapparatus was correct. The only possibility of control was to determineby traditional analytic methods the fatty content of a selection of themilk samples analyzed by the Milko-Tester.

For several reasons this method is inexpedient. The traditional analyticmethods are laborious, and it requires time before the results areavailable. The Ross-Gottlieb method produces the most accurate results,but they are not available until the day after the analysis has beencommenced. The results cannot therefore be used for a continuous controlor adjustment, but only for correction of the previous day'sMilko-Tester results. The Gerber method is less accurate, but theresults are available substantially earlier and may therefore be usedfor a fairly reliable adjustment and current control of theMilko-Tester. Both methods require skilled staff and extensivelaboratory equipment, which is unfortunate as the very idea of theMilko-Tester was to avoid this. Finally, as a disadvantage should bementioned the necessity of using a comparatively large number of milksamples for controlling the Milko-Tester.

One embodiment of the preparation according to the invention has provedto be particularly suitable for rapid control and adjustment of theMilko-Tester. As the preparation in many respects was to act as a milksample it was natural to base it on milk. As gelling agent gelatine wasfound to be particularly advantageous as its gelling ability iscompletely neutralized at temperatures above about 40 C., so that thepreparation may without difficulty pass through the Milko- Tester, whichitself heats the milk to 60 C. In accordance herewith a specificembodiment of the preparation according to the invention ischaracterized in that is consists of milk wherein at least 0.5 percentby weight of gelatine is dissolved.

To make the preparation resistant to microbiological decomposition itmay expediently contain preservatives. Among the preservatives sodiumbenzoate alone was found to be in capable of giving the preparationadequate keeping qualities. It was then tried to use also a substancehaving a strong bacteriostatic activity. According to the invention ithas been found to be particularly expedient together with the benzoateto use a quaternary ammonium compound, for instancealkyldimethylbenzylammonium chloride (trade name: Rodalon) in aconcentration of about 0.1 percent active substance in the preparation.

The preparation according to the invention may generally be prepared bya process which according to the invention is characterized in that anoil-in-water emulsion is admixed with a stabilizing agent dissolved inthe emulsion during heating, whereupon the mixture is cooled to form agel.

For preparing the particular embodiment of the preparation especiallysuitable for controlling and adjusting the Milko- Tester milk is used asemulsion and gelatine as stabilizing agent. A preferred embodiment ofthe process according to the invention is characterized in that milk isheated to about 40 C. or above whereupon at least 0.5 percent by weightof gelatine is added while stirring and the solution formed is hottledif desired after filtration.

With a view to the keeping qualities of the preparation it hasfurthermore been found to be expedient to subject the milk tolow-temperature pasteurization and, to prevent the fat from risingduring the pasteurization, to start with a mild homogenization of themilk.

The application of the preparation according to the invention forcontrolling and adjusting for instance the Milko- Tester may be carriedout as follows:

A few bottles of each production are drawn for determining the valuewhich it is desired to obtain for the contents of each bottle from theproduction in the Milko-Tester. The selected 3 4 bottles are placed in awater bath at 40 C. until the gel has readings on the Milko-Tester weretaken 2, 3, 5, 7, l2, 14, 20, melted (about minutes), whereupon thecontents of each and 26 days after preparing the two batches of thepreparabottle is measured 2 or 3 times on a correctly operatingMilkotion. 'lestcr. The average value is calculated, and the otherbottles Of the four Milko-Tester results of each bottle the first onefrom the production are marked with this value. The accurate 5 wasdiscarded with a view to possible errors due to carryovers.determination of the contents may, if desired, be made by The averagesofthe other three results are listed in table l.

using one of the conventional analytic methods.

The other bottles may now be used for controlling and ad- TABLE 1 uatmgother Mllko-Testers. The method is the following: Average of the Milko-rester results for W0 batches of A bottle is placed in a water bath asdescribed above, and 2 preparation each kept in homes for difieremperiods of time or 3 readings are taken on the Milko-Tester to becontrolled. at

Number of days stored 2 3 5 7 ll H Batch 1: Average of individualbottles. 3. 6!! 3. 67 3. 65 3.66 3. 65 3.66 3.61 3. 64 3. 65 3.63 3.633.63 3.65 3.63 3.64 3. 6'. 3.63 3. 64 3.63 3.62 3.65 3.65 3. 64 3.623.66 3.64 3.67 3.64 3.64 3.66 3.63 3.67 3.64 3.63 3.66 3. 64 3.65 3.633. 64 3.64 3.64. 3.66 3.63 3.64 3.63 3.65 3.65 3.64. 3.63 3.63 3.633.65. .364. .3.65 3.66.. 3.63 3.67 3.64 3.65

Daily average 3.65 3. 65 3.64 3.65 3.64 3. 65 3. 64

Batch 2zAvsrage0i1ndividual b0ttles.... 4.01 4.02 4.00 4.00 4.01 4.024.02 3. 99 4.02 4.00 4.00 4.00 4.00 4. 02

Dally average... .000 4.01 4.00 4.00 4.00 4. 00 4.00 4.00 If the averageresult differs from the value stated on the bot- As appears from thetable, the stress has been on determinatles, this variation may be usedas correction for the results of tions shortly after and l, 2, and 3weeks after the preparation the milk samples, and the Milko-Tester maybe adjusted to of the batches. The additional samples were used forsuppleshow the value stated. mentary measurings. The daily average isplotted in respectively FIG. 1 and FIG. 2 of the drawing, and it will beseen that EXAMPLE the variations are very small and occur within a veryrestricted Prepaflng the Preparation! interval, and the preparation musttherefore be considered very stable after storage at 8 C. for more than3 weeks.

To get an idea of the variation from bottle to bottle a calculation wasmade of the standard deviation from respectively the daily and the totalaverage for the days where readings were taken of many bottles, and forall the bottles from each batch collectively. These results are listedin table 2.

l: 12 liters of cold milk are admixed with 3 grams of sodium benzoateper liter.

2: The milk is heated to 50 C. and homogenized at at least 50 atm.

3: Low-temperature pasteurization (30 minutes at 63 C.).

4: The 40-50 C. warm milk is admixed with 20 grams of gelatine perliter. Stirring.

5: Filtration through a fine-mesh strainer. TABLE 2 6: Gradual admixtureduring stirring of ml. 2 percent 50 Average values and correspondingstandard deviations cal Roclalon (or other quaternary ammoniumcompound). l fid n th basis of table TABLE 2. AVERAGE \ALUEB ANI)CORRESPONDING STANDARD DE- vlATmNs CALCULATED ()N THE BASIS OF TABLE 1Number of days stored 7 All 2 7 14 20 results First IJHLI'II 0054:00210054:0015 3. 0540. 012 3. 64*0. 015 3. 64:0. 017 Slt'Olld butt-h a.004:0. 020 4.0040. 011 4.00:0.018 4.00;i;0.016 4 00:0.010 7: Tappinginto bottles of 200 ml. Table 2 shows that the standard deviation isbetween one and 8: Cooling in a water bath to 8-l0C. Cool storage.Notes: 60 two hundredths percent of fat, which is within the standardRaw milk of good bacteriological quality is used. It is impordeviationfor repeated measurings of the same milk sample tant that the admixtureof Rodalon takes place gradually and with the Milko-Tester. Thereforethere has been no significant during stirring as otherwise precipitationmay occur in the difference between the results of the individualbottles from milk. 65 the same batch of preparation.

Testing the preparation The testing did not include examinations of thekeeping To test the suitability of the preparation for controlling andqualities of the Preparation when at tampemmles adjusting theMilko-Tester it was examined whether a series of above but the stabilityof the gel "P to melting poi"t different samples from the sameproduction were so uniform at and the effect of the Preservation made itP d k so ll h aft r storage f diff r t i d f time ble that the sampleswould withstand storage for a shorter or they would give the samereading on the Milka-Tester. For the longer Period of time alsotempermllles above testing two separate batches of the preparation wereprepared No attempts were made to determine the fatty content ofaccording to the above directions and each tapped into 60 200 thepreparation by the traditional analytic methods, and it is ml. bottles.probably inadvisable to employ these methods for determining At few daysintervals a number of bottles from each batch the values desired for thesamples of the preparation on the were taken out from the cool store.After melting the gel four Milko-Testel' as h m g niz milk amples areknown to readings of each bottle were taken on the Milko-Tester. TheProduce MilkWTeSlel' results which iff r f m he Corresponding results ofthe Gerber and Rose-Gottlieb determinations. The safest method ofdetermining the values desired for the preparation on the Milka-Testerwill therefore be the method according to the directions stated.

The testing proved that by following the directions it was possible toprepare series of samples which were so uniform and kept so well whenstored at 8 C. that the samples showed the same result on theMilko-Tester more than three weeks after their preparation.

Later two batches of preparation were prepared by a procedure differingslightly from the aforesaid, namely in that the admixture of Rodalon wasmade first simultaneously with the admixture of benzoate, and thelow-temperature pasteurization was performed last on the filled andsealed bottles. This amended procedure should have no effect on theresults rendered by the preparation on the Milka-Tester, but shouldimprove its resistance to microbial decomposition. Bottles from the saidbatches were stored for four months at room temperature with no visiblesigns of any change.

We claim:

1. Method of calibrating an apparatus for determining the fatty contentof milk by measuring light transmission therethrough comprisingpreparing a mixture of milk and approximately one-half to two percentgelatin, dividing said mixture into a plurality of samples, subjecting anumber of said samples to an accurate determination of the fatty contentthereof, marking the remaining number of said samples with the fattycontent determined from said accurate detennination, and calibratingsuch apparatus by measuring the light transmission through at least oneof said marked samples.

2. Method defined in claim 1 further comprising heating said markedsamples to recover the normal liquid state of the mixture beforemeasuring the light transmission therethrough to calibrate theapparatus.

3. Method of preparing a sample for calibrating an apparatus fordetermining the fatty content of milk by measuring light transmissiontherethrough comprising, preparing a mixture of milk and approximatelyone-half to two percent gelatin, dividing said mixture into a pluralityof samples, subjecting a number of said samples to an accuratedetermination of the fatty content thereof and marking the remainingnumber of said samples with the fatty content determined from saidaccurate determination.

i i t i

2. Method defined in claim 1 further comprising heating said markedsamples to recover the normal liquid state of the mixture beforemeasuring the light transmission therethrough to calibrate theapparatus.
 3. Method of preparing a sample for calibrating an apparatusfor determining the fatty content of milk by measuring lighttransmission therethrough comprising, preparing a mixture of milk andapproximately one-half to two percent gelatin, dividing said mixtureinto a plurality of samples, subjecting a number of said samples to anaccurate determination of the fatty content thereof and marking theremaining number of said samples with the fatty content determined fromsaid accurate determination.